Abstract: Several protocols for fair exchange have been proposed in recent years，but some of them can’t achieve the fairness in payment.The new protocol proposed in this paper exchanges information of customers and merchants fairly in virtue of semi-trusted third party，and realizes fair payment based on a concurrent signature scheme.This protocol guarantees the fairness and non-repudiation of the whole transaction.And it can be applied to the trade of digital products in network environment.

摘要： 针对许多协议在网络环境下的数字产品交易中不能够同时实现信息交换及支付的公平性，提出一种新的公平交易协议，即借助STTP（半可信第三方）公平交换顾客与商家的交易信息，并在同时生效的签名基础之上实现支付的公平性。协议保证了交易过程的公平性与不可抵赖性，适用于网络环境下的数字产品交易。